Dissertations / Theses on the topic 'Refractory'
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Shealy, Benjamin L. "Refractory stories /." Connect to this title online, 2008. http://etd.lib.clemson.edu/documents/1219861866/.
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Akpan, Edem T. Gogot︠s︡i I︠U︡ G. "Viscoelastic toughening of refractory ceramics /." Philadelphia, Pa. : Drexel University, 2004. http://dspace.library.drexel.edu/handle/1860/284.
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Moulin, Silva Wagner. "Microsilica-bonded magnesia-based refractory castables." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2011. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-77492.
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Among the most impressive developments observed in the last 20 years, the improvement of the installation methods of monolithic refractories is certainly to be taken into account. However, this evolution, from vibratable castables to shotcrete and drycrete was not applied to materials based on magnesia, which are still mostly commercialized as ramming mixes, or as pouring castables with poor properties due to excessive water use. The major issues associated to this lack of technology is the scarcity of submicrometric powders compatible to magnesian systems, and the expansion followed by hydration of the magnesia, which is a disruptive reaction.
By a thorough research on the literature, some potential additives were identified to be tested as anti-hydration additives. Hydration tests of powders in autoclave, complemented by pH and rheological measurements on magnesia pastes have identified five possible additives which can be used to inhibit the hydration: tartaric acid, citric acid, boric acid, magnesium fluoride and microsilica. Salts from the organic acids can also be successfully used. Of these, microsilica also presented the advantage of providing the submicrometric particles necessary to improve the flow of the castable, and to improve the bond of the castable. The three acids are very effective in inhibiting the formation of magnesium hydroxide, but affect negatively flow properties and mechanical resistance after cure.
Microsilica prevented hydration cracks due to the reaction between the silicic acid generated under basic environment with the newly formed brucite, leading to the precipitation of a magnesium-silica-hydrated phase of poor crystallinity between the magnesia grains. This phase does not promote volumetric change, and also enable water release at a wider temperature range. Due to its nature close to serpentine minerals, it forms forsterite and enstatite at low temperatures, thus generating suitable strength between room temperature and at least 1400 °C.
Magnesium fluoride changed the nature of this magnesium-silica-hydrated phase, by being incorporated to it and forming a phase more similar to the humite minerals. These minerals present higher MgO:SiO2 molar ratio than serpentine, and their formation requires a lower content of microsilica for a same effect against hydration, which is beneficial for the overall properties of the castable.
The properties of the castable, as well as the influence of a number of other variables (for instance, refractoriness under load, creep, cold crushing strength, cold modulus of rupture, bulk density and apparent porosity) were also studied and hereby reported. It is believed that this technology can be further developed for industrial use, provided that some issues regarding the properties at high temperatures are solved. Not only had the study and comprehension of the nature of the bond between microsilica and magnesia, and the role of magnesium fluoride been pioneered by this work, but also the methodology used to evaluate the hydration after the drying process of castings, which was close to real refractory components.
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Kwan, Patrick Kwok Leung. "Refractory epilepsy : natural history and pathogenesis." Thesis, University of Glasgow, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250783.
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Fletcher, Helen Lucy. "Hydratable alumina for refractory castable systems." Thesis, University of Leeds, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400262.
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Al-Mashhadani, Hayder. "Refractory metals low temperature diffusion bonding." Universitätsverlag Chemnitz, 2018. https://monarch.qucosa.de/id/qucosa%3A33758.
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In this dissertation, the minimization of the diffusion bonding temperature during refractory metals’ diffusion bonding process was studied. Two pure refractory metals were used in this study: molybdenum and tungsten. The influence on the joint quality of molybdenum structural conditions, as well as molybdenum surface conditions, was examined. Moreover, diffusion bonding of tungsten to Oxygen Free Electrical copper and copper alloy (CuCr1Zr), without using an interlayer but instead using different bonding parameters, was evaluated. Diffusion bonding of tungsten to Oxygen Free Electrical copper and to CuCr1Zr alloy using titanium and nickel together as intermediate layers was also investigated, as well as the diffusion bonding of tungsten to Oxygen Free Electrical copper and to CuCr1Zr alloy using only nickel as an intermediate layer.
The resulting joints were evaluated using optical microscopy, SEM, hardness, shear, and tensile tests. The residual stresses, as well as the deformation, that are generated due to the diffusion bonding process were evaluated through a FEM simulation using the software ANSYS.
For pure molybdenum joints, successful results in minimizing bonding temperature were obtained. In tungsten to Oxygen Free Electrical copper and to CuCr1Zr alloy joints contrasting results were achieved.In dieser Arbeit wurde ein Diffusionsschweißverfahren durchgeführt, um zwei Refraktärmetalle zu verbinden. Das erste war Molybdän, das ähnlich diffusionsgeschweißt ist. Das zweite war Wolfram, das diffusionsgeschweißt an OFE-Kupfer und an die CuCr1Zr-Legierung gebunden ist. Aufgrund der hohen Schmelztemperatur von Molybdän und Wolfram erforderten sie eine hohe Diffusionsschweißtemperatur. Das Hauptziel dieser Arbeiten ist es, die erforderliche Temperatur für den Verbindungsprozess zu reduzieren. Die Reduzierung der Molybdän Diffusions-schweißtemperatur ist abhängig von den Bedingungen der Molybdänoberfläche und -struktur. Die Verbindung von Wolfram mit OFE-Kupfer und mit CuCr1Zr-Legierungen erfolgte direkt (ohne Zwischenschicht) sowie unter Verwendung von Titan und Nickel als Zwischenschicht(en). Das Verbinden mit Zwischenschicht(en) ist abhängig von den Interaktionen zwischen der Zwischenschicht und den Grundwerkstoffen. Die Zwischenschichtenmetalle waren Reintitan und Reinnickel. Das Aufbringen der Zwischenschichten in den Verbindungen wurde als Wolfram - Titan - Nickel - Reinkupfer oder CuCr1Zr sortiert. Außerdem wurde nur reines Nickel als Zwischenschicht verwendet, um Wolfram mit Kupfer und der CuCr1Zr-Legierung zu verbinden. Die chemische Zusammenstellung der CuCr1Zr-Legierung ist in der Tabelle 1 dargestellt. Die Eigenspannungen sowie die Verformung, die durch den Diffusionsschweißprozess sowohl für die Refraktärmetalle Molybdän als auch Wolfram erzeugt werden, wurden durch einen Simulationsprozess mit dem Programm ANSYS bewertet. Die resultierenden Verbindungen wurden mittels Lichtmikroskopie, REM, Härte-, Scher- und Zugversuch bewertet. Die Eigenspannungen sowie die Verformung, die durch den Diffusionsschweißprozess erzeugt werden, wurden durch eine FEM-Simulation mit der Software ANSYS bewertet. Für reine Molybdänverbindungen wurden erfolgreiche Ergebnisse bei der Minimierung der Diffusionsschweißtemperatur erzielt. In Wolfram zu OFE-Kupfer und zu CuCr1Zr-Legierungsverbindungen wurden kontrastreiche Ergebnisse erzielt.
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Masiá, Fandos Nuria. "Targeting mitosis in hormone-refractory prostate cancer." Doctoral thesis, Universitat Autònoma de Barcelona, 2020. http://hdl.handle.net/10803/670655.
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El CaP és la segona neoplàsia maligna invasiva diagnosticada amb major freqüència i la taxa de supervivència a 5 anys dels homes amb malaltia metastàtica cau per sota del 30%. Els andrògens, a través del receptor d'andrògens, són crucials per a l'inici i la progressió del CaP i, per tant, la ADT ha estat el principal tractament del CaP localment avançat, metastàtic i recurrent. Les teràpies de deprivació androgènica són capaces d'aconseguir inicialment una resposta bioquímica en la majoria dels pacients; no obstant això, les remissions són temporals i la malaltia acaba progressant a un estat independent d'andrògens, també denominat CRPC. Després de la progressió a CRPC, la supervivència mitjana d'aquests pacients és de menys de 2 anys i la malaltia acaba sent pràcticament intractable. Els mecanismes moleculars que causen aquesta transició continuen sent en gran part desconeguts.
La creixent evidència en els últims anys suggereix que les cèl·lules de CaP insensibles als andrògens han estat reprogramades genèticament per a regular de manera selectiva l'expressió de gens de la fase M del cicle cel·lular. Els taxans, dirigits als microtúbuls, ja s'estan utilitzant en la pràctica clínica per a pacients amb CaP avançat, però la supervivència continua sent modesta i els pacients acaben desenvolupant resistència a la teràpia. Pel fet que la progressió mitòtica és un procés altament regulat, la nostra hipòtesi és que les proteïnes de fase M expressades de manera aberrant poden conferir a les cèl·lules CaP un avantatge per al creixement en condicions de depleció d'andrògens i, en conseqüència, representen possibles dianes terapèutiques per a la intervenció molecular de pacients amb CRPC. Encara que diversos inhibidors del cicle cel·lular no han aconseguit demostrar benefici en l'entorn clínic del CRPC, continua havent-hi un gran interès en aquest enfocament i encara hi ha desafiaments importants per a intentar tractar a aquests pacients amb teràpies dirigides que siguin eficaces.
En aquest context, l'objectiu principal d'aquesta tesi és obtenir nous coneixements moleculars sobre la progressió del CaP, amb especial èmfasi en la participació dels reguladors mitòtics en l'adquisició de la independència a andrògens dels tumors de pròstata.El CaP es la segunda neoplasia maligna invasiva diagnosticada con mayor frecuencia y la tasa de supervivencia a 5 años de los hombres con enfermedad metastásica cae por debajo del 30%. Los andrógenos, a través del receptor de andrógenos, son cruciales para el inicio y la progresión del CaP y, por tanto, la ADT ha sido el principal tratamiento del CaP localmente avanzado, metastásico y recurrente. Las terapias de deprivación androgénica son capaces de conseguir inicialmente una respuesta bioquímica en la mayoría de los pacientes; sin embargo, las remisiones son temporales y la enfermedad acaba progresando a un estado independiente de andrógenos, también denominado CRPC. Tras la progresión a CRPC, la supervivencia media de estos pacientes es de menos de 2 años y la enfermedad acaba siendo prácticamente intratable. Los mecanismos moleculares que causan esta transición siguen siendo en gran parte desconocidos. La creciente evidencia en los últimos años sugiere que las células de CaP insensibles a andrógenos han sido reprogramadas genéticamente para regular de forma selectiva la expresión de genes de la fase M del ciclo celular. Los taxanos, dirigidos a los microtúbulos, ya se están utilizando en la práctica clínica para pacientes con CaP avanzado, pero la supervivencia sigue siendo modesta y los pacientes acaban desarrollando resistencia a la terapia. Debido a que la progresión mitótica es un proceso altamente regulado, nuestra hipótesis es que las proteínas de fase M expresadas de manera aberrante pueden conferir a las células CaP una ventaja para el crecimiento en condiciones de depleción de andrógenos y, en consecuencia, representan posibles dianas terapéuticas para la intervención molecular de pacientes con CRPC. Aunque varios inhibidores del ciclo celular no han logrado demostrar beneficio en el entorno clínico del CRPC, sigue habiendo un gran interés en este enfoque y todavía hay desafíos importantes para intentar tratar a estos pacientes con terapias dirigidas que sean eficaces. En este contexto, el objetivo principal de esta tesis es obtener nuevos conocimientos moleculares sobre la progresión del CaP, con especial énfasis en la participación de los reguladores mitóticos en la adquisición de la independencia a andrógenos de los tumores de próstata.
PCa is the second most frequently diagnosed invasive malignancy and the 5-year survival rate of men with metastatic disease drops below 30%. Androgens, through the AR, are crucial for the initiation and progression of PCa and thus, ADT has been the mainstay of treatment for locally advanced, metastatic and recurring PCa. Androgen-ablation therapies can initially achieve a biochemical response in the majority of patients; however, remissions are temporary and the disease invariably progresses to an androgen-independent state, also termed CRPC. Upon progression to CRPC, the median survival for those patients is less than 2 years, and the disease is essentially untreatable. The molecular mechanisms that cause this transition remain largely unknown. Increasing evidence in recent years suggest that androgen insensitive PCa cells have undergone a genetic reprogramming to selectively upregulate the expression of M-phase cell cycle genes. Microtubule-targeting taxanes are already being used in the clinical practice for patients with advanced PCa, but survival remains modest and resistance inevitably develops. Because mitotic progression is a highly regulated process, we hypothesized that aberrantly expressed M-phase proteins may confer PCa cells an advantage to growth in androgen-depleted conditions and consequently represent potential therapeutic targets for the molecular intervention of CRPC patients. Although several small molecule inhibitors of the cell cycle have failed to demonstrate benefit in the clinical setting of CRPC, there remains a keen interest in this approach and significant challenges persist to match patients with effective targeted therapies. In this context, the main goal of this thesis is to gain novel molecular insights into the progression of PCa, with special emphasis on the involvement of mitotic regulators in the acquisition of prostate tumors androgen independence.
Universitat Autònoma de Barcelona. Programa de Doctorat en Bioquímica, Biologia Molecular i Biomedicina
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Liang, Dawei. "Anaerobic degradation of toxic and refractory aromatics." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/hkuto/record/B3865023X.
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Strickland, Ben. "Personality and the psychological refractory period phenomenon /." Title page, contents and abstract only, 1997. http://web4.library.adelaide.edu.au/theses/09SB/09sbs917.pdf.
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Liang, Dawei, and 梁大為. "Anaerobic degradation of toxic and refractory aromatics." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B3865023X.
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Zargar, Hamidreza. "Sintering studies of magnesia-chromite refractory composites." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/46175.
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The magnesia-chromite refractory composites are the best candidates for the lining of non-ferrous metal smelting and refining furnaces, due to their high melting temperature, chemical inertness, and excellent thermal shock resistance. However, their high sintering temperatures (>1700°C) increase the processing complexity and costs. In this investigation, the primary goal was to study the sintering of these composites, with the long-term engineering goal to reduce their sintering temperature to <1500°C in air.
The materials were synthesized via chemical methods using nitrates to assure chemical homogeneity. Al₂O₃, Fe₂O₃, and SnO₂ affected the kinetics of the MgCr₂O₄ formation and increased the density of MgCr₂O₄ in the order Fe₂O₃>Al₂O₃>SnO₂. The enhanced MgCr₂O₄ densification was attributed to the cation distribution in spinel structure (inversion phenomenon), caused by the inherent affinity of Fe⁺³ and Al⁺³ to tetrahedral sites. Fe₂O₃ and Al₂O₃ showed to form inverted spinel, while SnO₂ resulted in the formation of normal spinel solid solutions.
Twelve magnesia-chromite composites were synthesized to study the effects of Al₂O₃, Fe₂O₃ and Cr₂O₃ on their sintering conditions; Cr₂O₃ decreased the density, while Fe₂O₃ and Al₂O₃ enhanced the densification of composites. The microstructural studies revealed that Fe₂O₃ and Al₂O₃ reduced the dihedral angle between MgO and spinel, while Cr₂O₃ increased it. The increased densification by Fe₂O₃ and Al₂O₃ was attributed to the decreased dihedral angle and formation of inverted solid solutions.
The optimized composition [MgO6.9Cr₂O₃6.9Al₂O₃2.7Fe₂O₃]mol% (MK) reached nearly full density in air at 1475°C for 70minutes; 1700°C is currently used for magnesia-chromite refractories.
In order to study the effects of the particle size on densification, magnesia-chromite composites (NMK) with average particle size of ~20 nm were synthesized via Pechini's method. Reducing the particle size from 1.2 um for MK to 20 nm for NMK reduced the onset sintering temperature by 200°C to 1000°C.
The densification results were evaluated using master sintering curve theory for the first time for this kind of composites. The sintering activation energy was 443.7 and 302.6 kJ/mol for MK and NMK respectively. It was hypothesized that the oxygen diffusion through lattice and grain boundaries was rate controlling mechanism for MK and NMK respectively.
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Sands, Christine M. "Dedicated finite element analysis for refractory composites." Thesis, University of Aberdeen, 2004. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=211271.
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This thesis presents a material model that has been designed to simulate the behaviour of certain refractory consumables used in the steel making industry. It is based on the principles of linear elasticity and isotropy, and a constitutive equation is developed that describes a non-linear mechanical response in tension with developing anisotropy. The mathematics of the model is firmly based on the physicality of the observed material behaviour, including the stable growth of microcracks. The residual stress that develops in some dual phase ceramics with thermal mismatch is quantified from the thermal properties of each phase and used to determine the change in the properties of the composite when undergoing damage as a result of cooling after firing and applied tensile stress. Energy principles and a crack orientation density function that can be plotted on the surface of a sphere are used to ensure that the model is invariant to changes in the reference axes, while a simplification to ensure that matrices are always positive definite ensures computational robustness. A one dimensional constitutive equation is developed and then extended through a single phase isothermal model to establish a three dimensional, dual phase, thermal model that was incorporated as a subroutine into a commercial finite element analysis package and can be used to simulate the behaviour of real components subjected to thermal and mechanical load. Creep at high temperatures was modelled, somewhat crudely, by reducing (effectively to zero) the stiffness and load carrying capacity of material that was operating at temperatures above a critical value. The computer subroutine was validated analytically and against physical tests that were conducted at room temperature. Appropriate high temperature material data was not available. The model's ability to simulate the observed features of the tests to a useful degree of accuracy with suitable material properties was demonstrated. An optimisation routine to enable the model to be calibrated quickly was developed. Finally the limitations of the model are explored and possible further work outlined.
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Dodd, Simon Peter. "An ultrasonic study of refractory hard ceramics." Thesis, University of Bath, 2002. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760795.
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Gentile, Maria. "Alkali attack of coal gasifier refractory lining." Thesis, Virginia Tech, 1987. http://hdl.handle.net/10919/45668.
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An experimental test system was designed to simulate the operating conditions found in nonslagging coal gasifiers. The reaction products that form when refractory linings in coal gasifiers are exposed to alkali impurities (sodium or potassium) were experimentally determined. Analysis of selected physical and chemical properties of the reaction products, which typically form between the alkali and the refractory will lead to a better understanding of the mechanisms behind refractory failures associated with alkali attack.
The reaction products sodium aluminate (Na₂O⋅Al₂O₃), N₂C₃A₅ (2Na₂O·3CaO·5A1₂O₃), nepheline (Na20â ¢Al203â ¢2SiO2), potassium aluminate, (K2Oâ ¢Al203), and kaliophilite (K2Oâ ¢Al203â ¢2Si02) were synthesized and their solubility in water and coefficients of linear thermal expansion were: measured. Of the compounds tested, the formation of potassium aluminate would be the most detrimental to the gasifier lining. The linear thermal expansion of potassium aluminate was 2.05% from room temperature to 800°C, which was twice as large as the other compounds. Potassium aluminate also possessed the highest solubility in water which was 8.893/L at 90°C.
Master of Science
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Soni, Vishal. "Phase Transformations in Refractory High Entropy Alloys." Thesis, University of North Texas, 2019. https://digital.library.unt.edu/ark:/67531/metadc1538735/.
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High entropy alloys (HEAs) based on refractory elements have shown a great potential for high temperature structural applications. In particular, the ones containing Al, exhibits a microstructure similar to the γ-γ' in Ni-based superalloys. While these alloys exhibit impressive strengths at room temperature (RT) and at elevated temperatures, the continuous B2 matrix in these alloys is likely to be responsible for their brittle behavior at RT. Phase stability of five such alloys are studied by thermo-mechanical treatments and characterization techniques using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Two of these alloys showed an inverted microstructure, where the disordered BCC phase becomes continuous, and therefore, they were characterized in detail using SEM, TEM, atom probe tomography (APT) and synchrotron x-ray diffraction experiments. The phenomenon of phase inversion lead to a better combination of strength and ductility as compared to the non-inverted microstructure.To enhance the stability of B2 intermetallic phase which provides the strength when present in a BCC matrix, multicomponent B2 phase compositions stable at 1000°C in some of the above studied alloys, were melted separately. The aim was to establish a single phase B2 at 1000°C and understand the mechanical behavior of these single-phase multicomponent B2 intermetallic alloys. These alloys exhibited a ductile behavior under compression and retained ~1 GPa yield strength at temperature up to 600°C. The ductile nature of these alloys is attributed to the change in bonding nature form directional to metallic bonding, possibly resulting from a significantly high configurational entropy compared to binary or ternary stoichiometric B2 compounds.
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Sun, Tawei. "Alkali attack of coal gasifier refractory linings." Thesis, Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/94471.
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Thermodynamic calculations are used to study the alkali reactions in coal gasifier atmospheres. The reactive alkali and sulfur species released from coal are first calculated at temperatures from 800 K to 1900 K and pressures from 1 atm to 100 atm. Four P-T diagrams are constructed for the stable alkali and/or alkali-sulfur species at differ-ent temperatures and pressures. Alkali vapors are generated by the reactions
Na₂CO₃(s) + 2C(s) = 2Na(g) + 3CO(g)
Na₂CO₃(s) + H₂O(g) + C(s) = 2NaOH(g) + 2CO(g)
or
K₂CO₃(s) + 2C(s) = 2K(g) + 3CO(g)
K₂CO₃(s) + H₂O(g) + C(s) = 2KOH(g) + 2CO(g)
The phases formed from alkali-cement, and alkali-sulfur-cement reaction are also predicted. For both 53% and 72% alumina cement, calcium aluminate (CaO•Al₂O₃) is decomposed by the reactions
CaO•Al₂O₃ + 2Na + 1/20₂ = Na₂O•Al₂O₃ + CaO
CaO•Al₂O₃ + 2K + 1/20₂ = K₂O•Al₂O₃ + CaO
or
CaO•Al₂O₃ + 2Na + l/2S₂ = Na₂0•Al₂O₃ + CaS
CaO•Al₂O₃ + 2K + 1/2S₂ = K₂•Al₂O₃ + CaSM.S.
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Lee, Kyoung-Ho. "Alkali attack on coal gasifier refractory lining." Thesis, Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/80163.
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For a given coal gasification atmosphere, the reactions between fired alumina-chromia solid solution refractories and alkali (sodium and potassium) with and without sulfur at varying alkali concentrations were thermodynamically calculated using the SOLGASMIX-PV computer program and the results were experimentally confirmed. In addition, the kinetics of alkali diffusion into the refractory were experimentally determined as a function of time and temperature.
The results, both experimental and theoretical, show formation of alkali-aluminate (Na₂O⋅Al₂O₃, K₂O⋅Al₂O₃) and β-alumina (Na₂O⋅11Al₂O₃, K₂O⋅11A₂O₃) compounds with formation of several metastable alkali compounds in a coal gasification environment. Sulfur did not appear to affect the reaction products. Alkali distribution into the alumina-chrome refractory is rapid and the formation of the Na₂O⋅Al₂O/K₂O⋅Al₂O₃ compounds cause large volume expansion from the reaction surface which causes poor thermal shock resistance and eventual refractory failure. The hot face of an alumina-chrome refractory in service in an alkali environment will be prone to failure by alkali attack.Master of Science
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Hodgson, David Brian. "Investigating new treatment options for refractory asthma." Thesis, University of Nottingham, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.664300.
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Patients with difficult to manage asthma and chronic cough are commonly seen by respiratory physicians in the NHS. This thesis describes three randomised trials which explore new treatment options for these difficult groups. Non-invasive markers of airway inflammation and function were measured before each trial to help determine likely responders. In the first study, 30 patients with asthma and eosinophilic inflammation were given two weeks of prednisolone and then randomised to receive either ciclesonide 360mcg or placebo twice daily for 8 weeks. Though the between- group differences were not significant several patients had changed their usual maintenance dose of prednisolone during the trial. When these patients were removed from the analysis there was a significant improvement sputum eosinophils with ciclesonide. There was no significant change in the marker of small airway inflammation, so it is possible that this effect was due to a general reduction in airway inflammation from the higher dose of inhaled steroids, rather than specifically targeting the small airways. In the second study, 28 patients with refractory asthma were given azithromycin 250mg or placebo three times weekly for six weeks in a randomised, cross-over design. Though significant improvements in airway hyper-responsiveness, asthma control and sputum neutrophils were seen with azithromycin, these changes were not significant when compared to placebo.
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Akram, Mohammed. "Bonding mechanism in a new refractory castable." Thesis, Aston University, 1996. http://publications.aston.ac.uk/9647/.
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Lohner, Kevin Andrew 1974. "Microfabricated refractory ceramic structures for micro turbomachinery." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/9479.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1999.Includes bibliographical references (p. 103-109).
The MIT Microengine Project was initiated in 1995 as a joint effort between the Gas Turbine Laboratory (GTL) and Microsystems Technology Laboratory (MTL) to develop a MEMS-based micro-gas turbine engine. The thermodynamic requirements of power-generating turbomachinery drive the design towards high rotational speeds and high temperatures. To achieve the specified performance requires materials with high specific strength and creep resistance at elevated temperatures. The thermal and mechanical properties of silicon carbide make it an attractive candidate for such an application. Silicon carbide as well as silicon-silicon carbide hybrid structures are being designed and fabricated utilizing chemical vapor deposition of relatively thick silicon carbide layers (10-100 [mu]m) over time multiplexed deep etched silicon molds. The silicon can be selectively dissolved away to yield high aspect ratio silicon carbide structures with features that are hundreds of microns tall. Positive mold, negative mold, and hybrid Si/SiC processing techniques appear to be feasible microfabrication routes with potential for increasing microengine performance. Research has been performed to characterize the capabilities of these processes. Specimens fabricated in the course of this research show very good conformality and step coverage with a fine (~0.1 [mu]m diameter) columnar microstructure. Surface roughness (Rq) of the films is on the order of 100 nm, becoming rougher with thicker deposition. Residual stress limits the achievable thickness, as the strain energy contained within the compressive film increases its susceptibility to cracking. Room temperature biaxial mechanical testing of CVD silicon carbide exhibits a reference strength of 724 MPa with a Weibull modulus, m =16.0. This thesis documents the design trades that led to the selection of CVD SiC as the primary candidate refractory material for the microengine, and the initial experiments performed to assess its suitability and guide future material and process development.
by Kevin Andrew Lohner.
S.M.
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Maganti, Harinad. "Polycomb-like 2 (Mtf2/Pcl2) Mediated Epigenetic Regulation of Hematopoiesis and Refractory Leukemia." Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/37251.
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The Polycomb Repressive Complex 2 (PRC2) epigenetically regulates gene expression by methylating lysine 27 on histone 3 (H3K27me3). While the role of PRC2 core members during hematopoiesis has been elucidated, the role of PRC2 accessory protein, Mtf2, has not been well characterized outside of mouse embryonic stem cells. To investigate the role of Mtf2 in vivo, we created a gene-targeted knockout mouse model. Using this model, we discovered that Mtf2 was a critical regulator of hematopoiesis and its loss within the hematopoietic cells leads to loss of global H3K27me3 levels at the transcriptional start sites (TSS) therefore leading to the overexpression of multiple signalling networks. These findings presented in the first part of my thesis place Mtf2 as a critical regulator of hematopoiesis and expand the role of Mtf2 beyond a canonical accessory PcG protein. While our murine studies revealed that the loss of Mtf2 did not cause leukemia in mice, our studies of MTF2 in human cells demonstrated that MTF2 deficiency within human Hematopoietic Stem and Progenitor Cells (HSPCs) causes a myelo-proliferative phenotype that is reminiscent of pre-leukemia. Furthermore, when we screened MTF2 expression within leukemic stem cell (LSC) enriched CD34+ CD38- cells isolated from primary Acute Myeloid Leukemia (AML) patient samples at diagnosis, we observed that MTF2 is miss-regulated in AML and its loss predicted refractory AML. Using MTF2 knockdown (KD) transcriptomic and ChIP-seq data, we drafted MTF2-PRC2 Gene Regulatory Network (GRN) in human HSPCs and LSC enriched cells. Finally, using the MTF2-PRC2 GRN, we uncovered a direct mechanism by which MTF2 regulates chemoresistance in AML and show that targeting this mechanism via MDM2 inhibitors sensitizes refractory AML to standard induction therapy. These findings presented in second part of my thesis demonstrate MTF2 as a novel prognostic marker for refractory AML and provide a novel therapy that helps target MTF2 deficient refractory AML.
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Hishida, Masashi, Kazuhiro Toriyama, Yoriko Yamashita, Shinya Akatsuka, Akemi Hayakawa, Shuhei Torii, and Yuzuru Kamei. "Omental Flap Closure of Refractory Wounds: Rat Model." Nagoya University School of Medicine, 2010. http://hdl.handle.net/2237/12913.
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Pandhari, Abhijit. "Modeling of thermal stress cycling in refractory materials." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/62359.
Full textAbstract:
In metallurgical reactors, the thermal stress field of refractories always changes with the heat transfer conditions at the hot-face. It is suggested that ‘thermally induced refractory cracking’ is often the primary cause of in-service refractory failure but quantitative support for this is lacking. The current work is focussed on studying this aspect by developing an experimentally validated thermomechanical model that considers refractory strength degradation under repeated thermal cycling.
A thermo-mechanical model has been developed with ABAQUS to predict thermal stress and damage in a refractory specimen subjected to thermal cycling. An experiment based on the “contact-conduction method” that uses a hot/cold metal block to heat/cool a refractory specimen was carried out to validate the model. The experiments were run for up to 3-cycles starting from cold- and hot-refractory specimens. Thermocouples were used to gather temperature data from refractory and steel block. An inverse heat conduction model was developed to predict the heat flux applied to the refractory specimen by the steel block based on the temperature history from the steel block. Ultrasonic testing was carried out on the refractory specimens before and after the thermal cycling tests.
The contact-conduction method was successful in creating significant thermal gradients in the refractory specimens. Thermocouples on refractory located at 1cm from the
steel-refractory show temperature variation of about 500°C and 575°C for cold- and
hot-refractory specimen, respectively after 3-cycles.
The model was capable of predicting the temperature changes and damage in the refractory material after multiple cycles. Ultrasonic velocity tests show significant change in the sound velocities in the areas experiencing thermal cycling, indicating significant micro-cracking damage in those areas. It was seen that with multiple cycles the damage penetrated further into the specimen, however the magnitude of the damage does not increase significantly.
Application to an example tundish operation indicated that the model was capable of analyzing an ideal preheating schedule and was capable of predicting the effect of idle time and multiple thermal cycles on the damage in refractories. However, to predict thermal spalling more precisely, an integrated model that considers the effect of thermal gradients, chemical reactions and mechanical loads is needed.Applied Science, Faculty of
Materials Engineering, Department of
Graduate
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Oakley, David Edward. "Simulation of tunnel kilns for firing refractory products." Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/38120.
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Cheng, Xu. "Inert refractory systems for casting of titanium alloys." Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/3838/.
Full textAbstract:
Research has been undertaken to develop new yttria slurry systems for use in mould face coats for investment casting TiAl alloy, solving the pre-gelation problems of commercial yttria slurry systems to increase slurry life. Meanwhile, the new face coats should also have excellent sintering properties, chemical inertness, surface finish and be easy to prepare. The processes of developing the new slurry started with the filler powder investigation by adding different sintering additives into the yttria powder to achieve good sintering properties. Then the best filler powder candidates were selected to make the slurry. Finally, the new face coat slurries were used to make the shell face coat and the chemical inertness of those shells were investigated through the sessile drop and investment casting. In the research, the filler powder and face coat sintering properties were quantified through density, dilatometer testing, X-ray diffraction (XRD) and microstructural change at different testing temperatures. The interaction of different face coat systems and the metal were identified using hardness tests, sessile drop contact angle and the microstructural change at the metal/shell interface. In this research, three water-based binder face coat systems containing YF\(_3\), Y\(_2\)O\(_3\)+0.5wt% Al\(_2\)O\(_3\)+ 0.5 wt% ZrO\(_2\) (YAZ), and B\(_2\)O\(_3\) additives were found to have similar or even better sintering properties compared to a commercial face coat. Meanwhile, they had long life.
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Tamer, Fouad G. "Compressive behavior of refractory ceramics at elevated temperatures." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/50281.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1989.Title as it appears in M.I.T. Graduate List, Feb. 1989: Compressive behavior of refractory ceramics at high temperatures.
Includes bibliographical references.
by Fouad George Tamer.
Ph.D.
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Lubaba, Nicholas C. H. "Microstructure and strength of magnesia-graphite refractory composites." Thesis, University of Sheffield, 1986. http://etheses.whiterose.ac.uk/10254/.
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The relationships between fabrication variables, microstructure and selected properties of carbon bonded magnesia-graphite refractory composite materials have been investigated. A novel optical microscope method of characterizing the morphology of flake graphites was developed and used to determine distributions of length and thickness and average aspect ratios for the four graphite samples used in the study. The compaction behaviour of magnesia alone and in combination with the flake graphites has been studied in some detail and the microstructures of the products elucidated. It is shown that the amount of magnesia of small particle size plays a significant role in determining the graphite-graphite contact area in the structure. An irreversible volume expansion is observed on firing composites, the magnitude of which can be related to the microstructure and the graphite content. A phenolic resin binder restricts this expansion. It is shown that the carbon binder does not bond to the graphite phase and only weakly, if at all, to the magnesia. Consequently the strengths and moduli are low and show only a small variation with graphite type. The effect of adding graphite to carbon-bonded magnesia is to lower the strength slightly, but increasing the graphite content from 20-30% causes a small increase in strength. Increasing the amount of carbon bond from pitch has little effect on strength at levels of 5-15% whereas over the range 5-13% the resin binder has a more pronounced effect. The most significant factor affecting the strength and modulus of fired composites is the amount of silicon or aluminium, added as oxidation inhibitors, which react to form carbide and nitride phases. Finally, a brief study of slag penetration shows that this can be reduced by decreasing the amount of oxide fines in the composite because of the changes in microstructure that, result.
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Nartowski, Artur Marek. "Solid state metathesis preparation of hard refractory ceramics." Thesis, University College London (University of London), 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394445.
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Davis, Robert Bruce. "Design and development of advanced castable refractory materials /." Full text open access at:, 2001. http://content.ohsu.edu/u?/etd,187.
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Bullard, Daniel Edward. "Processing of refractory oxides in a nonequilibrium plasma." Diss., The University of Arizona, 1993. http://hdl.handle.net/10150/186440.
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This investigation focuses on the uses of non-equilibrium plasmas to enhance the chemical reactions used in metallurgical process chemistry. The main emphasis of this work was the reduction of TiO₂ and FeTiO₃ in a hydrogen plasma. The plasma was maintained in a single resonant cavity using microwave energy (2.45 GHz). The reaction was monitored for volatile species by a quadrupole mass spectrometer. The extent of reaction during hydrogen reduction experiments was performed using an external standard X-ray diffraction technique. The effect of process variables (absorbed power, chamber pressure, time of plasma solid contact, applied voltages) on the extent of the reactions and the sample temperature were investigated. An investigation into the chlorination of TiO₂ in a chlorine plasma was also performed, however, the numerous side reactions that developed during these experiments made analysis difficult. Attempts were made to identify the volatile species from the mass spectra obtained during the chlorination experiments. The reduction of fused silica as a result of contact with the plasma is also investigated. Thermodynamic calculations suggest that the reduction proceeds by the formation of silane in the plasma; metallic silicon is formed by the subsequent thermal decomposition of silane in a non-oxidizing environment. A mechanism for the formation of silane is proposed. Finally, one proposed use for this technology is presented: The production of oxygen in situ form the lunar soil. Experimental values and thermodynamic data are used to develop a plasma process flow diagram for the production of oxygen. The mining requirements, the hydrogen flow rates and the power demands for this system are compared to more conventional process under consideration for the production of lunar oxygen.
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Ladner, Deborah Tillman. "Fitness of the transgenic malaria-refractory mosquito Anopheles gambiae." College Park, MD : University of Maryland, 2004. http://hdl.handle.net/1903/1991.
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Thesis (M.S.) -- University of Maryland, College Park, 2004.Thesis research directed by: Entomology. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Osman, Suhana Hanum. "The degradation of refractory mineral oil residues using bioreactors." Thesis, Loughborough University, 1998. https://dspace.lboro.ac.uk/2134/26875.
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This thesis is concerned with the biodegradation of oily sludges typically found at refinery sites as waste residues from the refining of mineral oil. Currently these type of wastes represent significant environmental risk. Current technology that addresses containment during treatment to regulate the release of volatile organic carbons and reduction of the polynuclear aromatic hydrocarbons in the sludge, is incineration. Incineration is a costly option and this research has shown that the same treatment standards as incineration is achievable through bioreactor treatment with the correct process and reactor design.
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Guan, Hongwei. "Fractionated reaction time using the psychological refractory period paradigm." [Bloomington, Ind.] : Indiana University, 2005. http://www.oregonpdf.org.
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Tan, Keng Ean. "Quantum mechanical modelling of refractory transition metal carbide films." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294188.
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Jantan, Mohd Dahlan. "Chemical preservation of some refractory timber species of Malaysia." Thesis, University of Portsmouth, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310381.
Full textAbstract:
The treatability of six Malaysian timbers namely Red Balau (Shorea guiso), Kapur (Dryobafanops aromatica), Kasai (Pometia pinnata), Kulim (Scorodocarpus borneensis), Kempas (Koompassia malaccensis) and Keruing (Dipterocarpus grandiflorus) using the applied pressure processes (oscillating pressure, conventional Bethell and a modified Bethell process) was investigated. Treatments were carried out with a commercial water-borne copper-chromearsenic (CCA) preservative, known as Celcure-AP. The conventional Bethell process was the most effective method of wood treatment followed by the modified Bethell and the oscillating pressure process. While sufficient preservative retention and absorption was achieved in Kempas and Keruing to meet the Malaysian Standard MS 386 : 1986 specifications for exterior timber used in ground contact, the other four timbers - Red Balau, Kapur, Kasai and Kulim did not fulfil this requirement, even when treated at the most extreme treatment conditions. Using the three pressure processes, seasoning period and treatment time were found to have significant effects on preservative retention and penetration in all timber species. Investigations into the effect of three pretreatment procedures - steaming, incising and ponding to improve the treatability of the six timber species were carried out. Incising was the most effective pretreatment procedure in enhancing the treatability of these timbers. However, at the highest incising density employed (4,500 incisions/m2), it was still not possible to treat Red Balau, Kapur, Kasai and Kulim timber to achieve satisfactory target preservative retention and penetration. The less effective incising procedure was due mainly to the low incising density used. The possibility of improving the treatability of these four timber species further using higher incising densities and other methods of inCising pretreatment is discussed. Steaming, incising and ponding pretreatments had a pronounced effect on the strength properties of timbers based on reduction of their modulus of elasticity (M.D. E.), modulus of rupture (M.O.A.), compressive strength and hardness. The highest strength losses were observed in timbers that had been ponded for 6 months. Significant strength losses were also observed in incised and steamed timbers, but the magnitudes were lower than the 6 month ponding regime. This was attributed to low incising density and the short steaming period. The performance of Celcure-AP in the six timber species was evaluated in laboratory and field tests. In addition, a copper-azole formulation (Tanalith-3485) was also evaluated on Kempas timber. Laboratory tests involved exposure of treated wood blocks to five decay fungi - Pycnoporus sanguineus, Trametes versicolor, Coniophora puteana, Gloeophyllum trabeum and Oligoporus placenta. The less durable timbers - Kempas and Keruing needed a higher loading of Celcure-AP in order to give equal performance compared to the more durable timbers - Red Balau, Kapur, Kasai and Kulim. Based on copper retention in treated samples, a higher loading of Tanalith-3485 was required in Kempas to achieve comparable results to Celcure-AP treated samples. However, the concentration levels of Tanalith-3485 used in the present study were sufficient to afford protection to Kempas stakes exposed for 36 months in the field test. A longer exposure period is however, recommended for a full evaluation of timber/preservative combinations against wood deteriorating organisms under Malaysian conditions. In the field test, soft rot fungi were the main causal organisms in the attack of timbers in test site A (fungal test bed), while in test site B stake failure was due mainly to termite attack.
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Sillo, C. E. "Microstructural and chemical studies of stainless steel/refractory interactions." Thesis, University of Sheffield, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.291003.
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Arayarat, Pornthip. "Refractory products based on the pore reduced cement technique." Thesis, University of Aberdeen, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245256.
Full textAbstract:
The present study was aimed at an investigation of the use of the pore reduced cement (PRC) technique on the fabrication and properties of calcium aluminate-based refractories. Physical and chemical performances were compared with those of conventionally prepared (unpressed) refractory castables. The influence of firing on two types of calcium aluminate cements; (Ciment Fondu and Secar 80), mixed with aggregates such as firebrick and alpha-alumina, were observed. Most of the pressed samples based on Ciment Fondu cracked and melted during firing to 1250oC. Pressed samples based on Secar 80, however, tended to crack less with increased tabular alumina content. An appropriate weight proportion of tabular alumina and Secar 80 was found to be 70 to 30. The physical properties of Secar 80 blended with (i) tabular aluminas (20-μm and 250-μm) only and (ii) round (RMA325) and 250-μm tabular alumina were investigated before and after firing to 1350oC. Pressed tabular alumina mixes containing various percentages of aggregate showed very little change in bulk density (3000 kg/m3) and flexural strength (23 MPa), but after firing, flexural strengths increased considerably as the fine tabular alumina content increased (up to 50 MPa). Microstructural evidence indicated that the interlocking structure occurring from the crystallisation of hexagonal plates of calcium hexaluminate including partial sintering of fine alumina grains could be the origin of the increased strength on firing. Although unpressed samples show similar structures, they are more porous. On firing, unpressed samples tended to expand (0.43 to 0.64%) less than pressed samples (1.32 to 1.71%) because the phase transformation from CA2 to CA6 occurred which in pressed samples leads to expansion whereas in unpressed products, expansion is accommodated within available porosity. Abrasion resistance increases as strength increases. Fracture toughness increases with the coarse tabular alumina content increases. Similar improvements in bulk density and flexural strength are observed when round alumina (~ 44μm) and tabular alumina (250-μm) are blended. The thermal shock resistance of pressed samples was also found to be better than for unpressed samples as shown by the higher relative strength after the test. The chemical durability of unpressed and pressed samples based on the slag test was investigated. Pressed samples resist slag penetration better than the unpressed samples because of the smaller pores and reduced pores connectivity. Otherwise, chemical interaction between cement and slag was similar. In conclusion, refractory products based on the PRC technique have shown considerable improvements in both physical and chemical performance, especially green strengths which are substantially higher than for conventional castables, making them less susceptible to handling damage prior to service, i.e. during transport and installation.
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Martin, Rachel (Rachel M. ). "Mechanical testing of rapid-prototyping refractory ceramic print media." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/86278.
Full textAbstract:
Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, February 2013.Page 30 blank. Cataloged from PDF version of thesis.
Includes bibliographical references.
Additively manufactured (3D-printed) refractory alumina-silica ceramics were mechanically tested to ascertain their ultimate tensile strengths and observed to determine their dimensional consistency over the printing and post-printing process. The equipment used to perform tensile testing was designed and built for use with custom-designed tensile test samples. Two ceramic powders, V18 (electronic-grade alumina, colloidal silica, and organic content) and 403C (200-mesh mullite, organic content, and magnesium oxide), were printed into test samples on ZCorporation ZPrinter® 310 and 510 machines, before being infiltrated with tetraethylorthosilicate (TEaS), and in some cases infiltrated again with a 40% by weight suspension of silica in water (Ludox). Ludox-infiltrated V18 proved to be the strongest medium, with a UTS of 4.539 ± 1.008 MPa; non-Ludox-infiltrated V18 had a UTS of 2.071 ± 0.443 MPA; Ludox-infiltrated 403C was weakest with a UTS of 1.378 ± 0.526 MPa. Within V18, greater silica content lead to greater tensile strength, but this did not hold true for 403C. 403C displayed volumetric shrinkage of about 1.5%, while V18's volumetric shrinkage ranged from 7% to 14%.
by Rachel Martin.
S.B.
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Ruddick, Andrew. "Assessment and mechanism of the refractory period in asthma." Thesis, University of Leicester, 2015. http://hdl.handle.net/2381/31836.
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Hypothesis: The primary hypothesis of this thesis is that the refractory period in asthma is due to release of bronchoprotective mediator(s) within the airway and that these may be one or more of the pro-resolving lipid mediators such as lipoxins or resolvins. Methods: 1. Development of a LC-MS assay for the detection of pro-resolving mediators in sputum. 2. Development of an in vitro airway model using porcine and human bronchial rings. 3. A clinical study of mannitol-induced refractoriness with collection of urine and sputum to assess changes in prostaglandin and pro-resolving mediator levels. Key Results: 1. Approximate LC-MS limits of detection were 0.002, 0.01 and 0.04 pg/μl for PGE2, LXA4 and RvD1 respectively. These LOD compare favourably with ELISA. 2. Serial LC-MS analysis of spiked sputum samples showed that LXA4 appeared stable, while PGE2 and RvD1 showed some degradation over 5 months. 3. LXA4, RvD1 and MaR1 had no significant effect on the histamine response of porcine bronchial rings. 4. Bronchoconstriction with high concentration mannitol rendered an airway refractory to further contraction with direct ASM agonists via an unknown mechanism. 5. In human bronchial rings, neither 10 nM LXA4 nor 10 nM MaR1 had any effect on bronchoconstriction induced by mast cell FcμR1 activation. 6. In the clinical study, with bolus dosing the mean refractory index for mannitol was 24%. The degree of refractoriness to mannitol did not correlate with markers of disease severity. 7. Urinary PGD2 and PGE2 metabolite levels measured by ELISA showed no significant change in response to mannitol challenge. Sputum LXA4 and RvD1 levels measured by ELISA showed no consistent change in response to mannitol challenge. Conclusions: This study has found no evidence of a role for pro-resolving mediators in the mechanism of refractoriness.
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Van, der Westhuizen Carl Johan. "Outsourcing : understanding the strategic value in the refractory industry." Thesis, Stellenbosch : Stellenbosch University, 2008. http://hdl.handle.net/10019.1/970.
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Thesis (MBA (Business Management))--Stellenbosch University, 2008.ENGLISH ABSTRACT: RHI Refractories believe that the process of outsourcing certain activities of a companies’ value chain goes hand in hand with a complete new way of how management think and do things. The process of outsource the refractory activity of a company’s value chain is not just a matter of outsourcing a part of the value chain that cannot influence the company’s performance negatively, but it can stop the process. To achieve a true business relationship RHI and SASOL must have the same goals in their goal setting to make the contract successful. RHI Refractories and SASOL shared goals: • The target to reduce the Total Cost of Ownership involving the refractory material on SASOL. • Both parties need a 100% buy-in in this concept and need to lay down a guideline on mutual profit sharing to end up with a win-win scenario. • RHI to supply SASOL with a competent installation crew and technical assistance in exchange for remuneration. • RHI and SASOL to have a long term relationship to ensure installation crew is familiar with plant conditions on contract work as well as project work. RHI Refractory’s strategy to supply the service has two major advantages: a. these type of contract ensures a constant monthly cash flow; b. It lifts the entry barriers for rival companies that they are unable to compete cost effective on additional project work that’s not part of the outsourcing contract scope. From the financial results RHI was successful in their strategy by securing 100% of all the material and additional project work on the SASOL site. RHI wanted to establish a relationship that can be classified as – NETWORK ORGANIZATION. This relationship would better the marketing position of RHI Refractories, it would secure a long term relationship, both companies would benefit from a shared vision and this would lead to a win-win situation. RHI Refractories definitely benefit from outsourcing contracts as a service provider and in the same way it controls rival companies by setting high entry barriers through cost sharing between contract and project work.
AFRIKAANSE OPSOMMING: RHI Refractories glo dat die proses van uitkontraktering van sekere aktiwiteite van 'n maatskappy se waardeketting 'n kompleet nuwe wyse is waarop bestuur dink en besigheid doen. Die proses van uitkontraktering van die vuurvaste funksie van 'n maatskappy se waardeketting is nie net 'n geval van uitkontraktering van 'n gedeelte van die waardeketting wat die maatskappy negatief kan beinvloed nie, maar dit kan die proses stop. Om 'n ware besigheidsverhouding te verkry, moet RHI en Sasol dieselfde doelwitte in hulle doelstelling hê om die kontrak suksesvol te maak. RHI Refractories en SASOL se gedeelde doelwitte: • Om die Totale Koste van Eienaarskap te verminder ten opsigte van vuurvaste materiale; • Beide partye moet 100% inkoop in die konsep en moet riglyne neerlê vir wedersydse winsdeling wat lei tot ‘n wen-wen verhouding; • RHI moet SASOL voorsien van 'n bevoegde installasie span en tegniese bystand vir vergoeding; • RHI en SASOL moet 'n langtermyn verhouding opbou om te verseker dat die installasie span vertroud is met die aanleg omstandighede, kontrak- en projekwerk. RHI se strategie om 'n diens te verskaf het twee groot voordele: • Hierdie tipe kontrakte verseker ‘n konstante maandelikse kontantvloei; • Dit lig die intree vlakke van mededingende maatskappye in so ‘n mate dat mededingende maatskapye nie koste doeltreffend kan meeding op projekte wat nie deel is van die bestaande kontrak nie. Vanuit die finansiele resultate is dit duidelik dat RHI suksesvol was in hulle strategie deur 100% van alle materiaal en projekwerk verkry het op die SASOL aanleg. RHI wil ’n verhouding bewerkstellig wat geklassifiseer kan word as – NETWERKVORMEND. So ’n verhouding sal ’n beter bemarkingsaanslag vir RHI beteken, dit sal ’n langtermyn verhouding verseker, beide maatskappye sal voordeel trek uit ’n gedeelde doelwit wat sal lei tot ’n wen-wen verhouding. RHI trek voordeel uit uitkontrakteerde kontrakte as ’n diensleweraar en in dieselfde tyd beheer dit mededingende maatskappye deur die intreevlakke te beheer deur kostedeling tussen kontrakwerk en projekwerk.
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Baxter, Derek. "Clinical and epigenetic factors underlying treatment refractory Rheumatoid Arthritis." Thesis, University of Glasgow, 2014. http://theses.gla.ac.uk/5608/.
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Rheumatoid Arthritis (RA) is a chronic, progressive, multisystem inflammatory disorder for which there is, at present, no cure. It affects up to 1% of the population resulting in chronic pain, disability and, through loss of function, may lead to loss of employment. It is associated with major co-morbidities that account for premature mortality. There is now extensive published research that suggests early treatment with disease modifying drugs can retard joint damage and improve outcome. In a proportion, drug- free remission is possible. However, there remain both individuals with persistently active disease despite standard drug treatments and those with longstanding disease not exposed to effective early treatment that remain relatively unresponsive to therapy. There is a growing literature that epigenetic modifications may underpin, or at least accelerate the development of many autoimmune disorders. These include alterations in DNA methylation patterns, histone tail modifications, post-translational mRNA regulation by microRNA and combinations therein. Having established the human genome project and underlying human DNA sequence, the recognition of dynamic epigenetic regulation of the genome has added further complexity. Few data however are currently available in ‘real-world’ cohorts of patients. In order to explore the hypothesis that specific epigenetic changes may underpin differences in response to therapy, I first examined the characteristics of a cohort of fifty RA patients with longstanding and active disease (DAS28 >3.2) despite receipt of standard therapies (disease modifying drugs (DMARD) and biologic therapies. This included a detailed examination of clinical characteristics, immune profile, inflammatory markers and burden of co-morbid complications such as vascular disease and depression. Outcomes such as disability, quality of life assessments and fatigue were evaluated by means of previously validated questionnaires. These groups were assessed at baseline, three months and six months. I then measured one of the many epigenetic marks, namely microRNA, of this cohort. We analyzed the accessible profile of peripheral RA CD14+ cell microRNAs in treatment resistant RA patients, in healthy controls, DMARD inadequate responders and DMARD good responders in order to determine the presence of a microRNA profile indicative of biologic resistance. An analysis of the serum cytokine profile of the biologic resistant and DMARD resistant groups was also performed. Finally, to extend the analysis beyond conventional clinical and novel molecular biomarkers the influence of additional patient factors such as coping and illness perception were evaluated by questionnaire to determine subjective disease severity in discrete patient groups. Active inflammatory disease was present as judged by the DAS28 score and there was some improvements seen over the six-month assessment period reflecting treatment changes in all groups. Substantial disability and impaired quality of life was found particularly in the therapeutic resistant group but also in those with inadequate response to DMARD, and remained relatively unresponsive to treatment escalation. Clinical variables, deprivation, quality of life and fatigue were strongly correlated with mood suggesting close interactions and resultant increase in disease activity as measured by the DAS28. Multiple cardiovascular risk factors were determined and, having applied cardiovascular risk scoring systems, unmet treatment of modifiable risk was demonstrated. Exploratory analysis of candidate microRNA -34a, -27b and -125a showed no correlation with clinical or biochemical variables other than swollen joint counts but differential expression between study groups. Exploratory microarray profiling between the four study groups demonstrated a number of differentially regulated microRNA. Of these, a unique microRNA profile of the biologic resistant group was found. MicroRNA-423 and -1275 showed higher expression in the biologic resistant group and fell in parallel with the DAS28 reduction between study visits raising their potential utility as biomarkers. MicroRNA-3178 showed higher relative expression in the biologic resistant group. Cytokine profiles demonstrated significant differences vs healthy controls but biologic resistant, DMARD resistant and DMARD good responder groups were less distinct and individual cytokines failed to discriminate in these study groups. Cytokine profiling did not correlate with observed clinical variables, inflammatory markers nor central processes such as mood or fatigue. Finally, those coping strategies favoured were adaptive and problem based. These were unaffected by the high prevalence of mood disturbance. Conversely, illness perception was influenced by mood and both affected subjective disease assessments. The strong influence of mood and fatigue raise the hypothesis that blunted treatment response may be partially driven by these variables. Ultimately we seek to explain, identify and target those patients with aggressive disease as early intervention may prevent established disease and it's accompanying co-morbid conditions. Undoubtedly, a personalised assessment of disease variables and co-morbid conditions is necessary where treatment response is being evaluated. In such a way, significant cardiovascular morbidity and mortality may be prevented. The question of true biologic resistance remains open. Undoubtedly residual inflammation exists in longstanding RA but significant ‘disease activity’ may be explained at least in part by those subjective clinical variables influenced by both external and internal factors. The identification of a ‘biologic resistant’ microRNA profile could act both as a biomarker of treatment response in longstanding disease, superior to the DAS28 scoring system and, through target identification, better understanding of the regulation of the molecular pathways of inflammation operating in such patients. In this way novel pathways of treatment resistance may be exposed and novel treatment targets revealed. However, mood and thus illness perception also contribute to resistance to therapy and should be sought, characterized, and directly addressed to add to the global improvements in outcome that we seek in a holistic model of care in the rheumatic diseases.
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Kummari, Rani S. "Improved SiC Schottky Barrier Diodes Using Refractory Metal Borides." Connect to resource online, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1266422079.
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Gentile, Paul Steven. "Investigation of aluminosilicate refractory for solid oxide fuel cell applications." Diss., Montana State University, 2010. http://etd.lib.montana.edu/etd/2010/gentile/GentileP1210.pdf.
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Stationary solid oxide fuel cells (SOFCs) have been demonstrated to provide clean and reliable electricity through electro-chemical conversion of various fuel sources (CH₄ and other light hydrocarbons). To become a competitive conversion technology the costs of SOFCs must be reduced to less than $400/kW. Aluminosilicate represents a potential low cost alternative to high purity alumina for SOFC refractory applications. The objectives of this investigation are to: (1) study changes of aluminosilicate chemistry and morphology under SOFC conditions, (2) identify volatile silicon species released by aluminosilicates, (3) identify the mechanisms of aluminosilicate vapor deposition on SOFC materials, and (4) determine the effects of aluminosilicate vapors on SOFC electrochemical performance. It is shown thermodynamically and empirically that low cost aluminosilicate refractory remains chemically and thermally unstable under SOFC operating conditions between 800°C and 1000°C. Energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) of the aluminosilicate bulk and surface identified increased concentrations of silicon at the surface after exposure to SOFC gases at 1000°C for 100 hours. The presence of water vapor accelerated surface diffusion of silicon, creating a more uniform distribution. Thermodynamic equilibrium modeling showed aluminosilicate remains stable in dry air, but the introduction of water vapor indicative of actual SOFC gas streams creates low temperature (<1000°C) silicon instability due to the release of Si(OH)₄ and SiO(OH)₂. Thermal gravimetric analysis and transpiration studies identified a discrete drop in the rate of silicon volatility before reaching steady state conditions after 100-200 hours. Electron microscopy observed the preferential deposition of vapors released from aluminosilicate on yttria stabilized zirconia (YSZ) over nickel. The adsorbent consisted of alumina rich clusters enclosed in an amorphous siliceous layer. Silicon penetrated the YSZ along grain boundaries, isolating grains in an insulating glassy phase. XPS did not detect spectra shifts or peak broadening associated with formation of new Si-Zr-Y-O phases. SOFC electrochemical performance testing at 800-1000°C attributed rapid degradation (0.1% per hour) of cells exposed to aluminosilicate vapors in the fuel stream predominately to ohmic polarization. EDS identified silicon concentrations above impurity levels at the electrolyte/active anode interface.
'Co-authored by Paolo R. Zafred, Stephen W. Sofie, Camas F. Key, and Richard J. Smith.'
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Carlsson, Mats. "Preparation and characterisation of refractory whiskers and selected alumina composites." Doctoral thesis, Stockholm : Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi, Univ, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-113.
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Rauh-Adelmann, Christine. "Newly-identified potential therapeutic targets for hormone-refractory breast cancer /." Thesis, Connect to Dissertations & Theses @ Tufts University, 1999.
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Thesis (Ph.D.)--Tufts University, 1999.Adviser: Shuk-Mei Ho. Submitted to the Dept. of Biology. Includes bibliographical references (leaves 169-171). Access restricted to members of the Tufts University community. Also available via the World Wide Web;
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Holford, W. David (William David). "A measurement technique for refractory erosion/corrosion in molten metals /." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63327.
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Bremner, Alasdair. "An investigation into the potential creative applications of refractory concrete." Thesis, University of Central Lancashire, 2008. http://clok.uclan.ac.uk/8797/.
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Refractory concretes (RC) are industrial materials used most commonly in high temperature applications, primarily in the steel and glass industries. In most cases they are a mix of refractory aggregate’s chosen for specific hot engineering applications combined with a cement binder. RCs are known to ceramicists largely only for their insulating properties for which they are used in the manufacture of kilns as hot face lining. However, currently very little information is available regarding the structural and aesthetic possibilities that RC can offer to the artist and designer. It is the researcher’s view that refractory concrete displays novel handling properties that include: increased green and fired toughness and strength, thermal shock resistance, ceramic glaze compatibility, thixotropic effects and rapid setting. These properties offer the opportunity to achieve the creation of objects that do not conform to some of the traditional limitations of conventional clay. This research asks whether new products and visual qualities might be achieved by the adoption of these materials in a sphere different from their intended industrial application. The thesis demonstrates these properties through a series of practice based projects each designed to capatilise on the unique and novel capabilities of RC. The objective was to develop new and innovative products some of which have architectural or urban design applications. In response to the applications developed through the practice elements of the research, two quantiative studies were conducted. New data on RCs resistance to freeze-thaw and slip resistance was generated both confirming that RC is fit for purpose in the proposed applications. Throughout the research the RC industry has been an integral source of both materials and expertise. This collaborative relationship is seen as generating knowledge transfer opportunities between industry and academic research. The research acknowledges the limitations of a single researchers approach and tackles this deficiency by engaging other professional artists and designers in the form of four case studies. The results of the case studies are evaluated using structured interviews. The practice based elements of the research are combined with quantitive research conducted to demonstrate the viability of RC as both a material with creative potential in the ceramic studio, and in the architectural and design sphere.
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Matin, Kamran. "The refractory transformation : the international relations of the Iranian Revolution." Thesis, University of Sussex, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496777.
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The academic discipline of International Relations (IR) remains largely distinguished by its paradigmatic self-definition contra sociological studies. Historical sociological approaches within IR have challenged this disciplinary insularity through highlighting the social determination of the historical modalities of international relations. Yet they generally remain uncritical of social theory's own tendency to de-conceptualise 'the international' as contingent. The present thesis is largely addressed to this theoretical omission. It argues that 'the international' is heavily constitutive of 'the social'. It empirically substantiatest his claim through a reinterpretation of the Iranian Revolution critically drawing on Leon Trotsky's theory of 'uneven and combined development' (U&CD). The thesis proceeds via a series of critical engagements with the sociological categories through which Iran's political history has traditionally been analysed. These include 'Asiatic mode of production', 'bourgeois revolution', 'Bonapartism', nationalism', 'rentier state' and 'political Islam'. In each case it is shown that the 'internalist' constitution of the category in question a priori omits an 'external' co/over-determination of the specific aspect or conjuncture concerned. The causality of this under-theorised international dimension is concretely manifest in the various hybrid patterns of development whose contradictions ultimately fuelled the socio-historical dynamics culminating in the 1979 revolution. The thesis therefore demonstrates that international relations have reached more deeply into the historical production of the revolution than the explicit record of Iran's foreign relations, the main focus of the conventional accounts, would suggest.
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Barran, Perdita Elizabeth. "Studies of refractory clusters produced from a pulsed arc source." Thesis, University of Sussex, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244325.
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Vega, Villanueva Karen, Nathaly Cortez-Bazán, and Angela Alvarado-Molina. "The use of ustekinumab in refractory treatment of psoriatic arthritis." Brazilian Society of Rheumatology (BSR), 2014. http://hdl.handle.net/10757/314834.
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